This invention relates to form systems and is more particularly concerned with the ties and brackets utilized in maintaining a pair of laterally spaced form boards in a predetermined position relative to each other for the reception of concrete.
Poured concrete will generate pressure of approximately 160 pounds per square foot of depth, with the inevitable result that forms of any substantial size will require securing systems of tremendous strength. The most reliable of these involves an imbedded tie rod extending across the space between the forms, and which is submerged when the concrete is poured. This tie rod is threaded at both ends and is engaged by bolts traversing the form panels and secured to the reinforcing beams supporting the panels. The pressure against each of the opposite form systems is thus equalized. The cross-sectional dimensions of each of the tie assemblies in interrelated with the spacing of them so that the concrete pressure is effectively resisted.
Other known ties have their snapties equipped to receive special wedges which engage the outer surface of the walers or other stiffening members employed. These ties are usually equipped with spacing elements to hold the form panels apart before the concrete is poured and it is common practice further to provide the ties with reduced neck portions whereby the ends of the ties may be broken off beneath the surface of the concrete after the concrete has hardened.
Form systems are used primarily by commercial contractors and the overall cost of the procurement and use of the forms is therefore highly important. The initial cost of the form structure, having in mind the degree of re-use for which it is designed, must be considered along with the erection time of the form determined primarily by its tie system and also the stripping time required to disengage the tie system and remove the forms from the completed concrete wall. Accuracy of spacing is obviously important in order to preserve the dimensional continuity of the wall surface.